This invention relates generally to X-ray imaging systems of the type employed for performing various X-ray examination procedures, including positioning for lithrotripsy, and more specifically to a dual-slide support mechanism for permitting extended travel of image intensifier and X-ray tub components of such systems. Known X-ray imaging systems employ a C-shaped arm, encompassing a patient table, for supporting an image intensifier and an X-ray tube in alignment with each other at opposing ends of the C-shaped arm. These prior art X-ray imaging systems provide for only 8-12 inches of travel of the image intensifier, for example, based upon the restriction that the support mechanism providing travel not extend beyond the ends of the image intensifier itself when the image intensifier is positioned in the center of its permitted range of travel. Since the amount of X-ray radiation required to perform a specific procedure increases as the cube of the distance between the patient and the image intensifier, it is important, in order to minimize the amount of X-ray radiation to which the patient is exposed, to position the image intensifier as near the patient as possible. Additional travel of the image intensifier is also required for parking the image intensifier in bi-plane X-ray imaging systems. It is also necessary, in some applications, to position the image intensifier underneath the patient table, thereby also requiring greater travel of the image intensifier than is possible in prior art X-ray imaging systems. These requirements dictate that the image intensifer be permitted to travel over a range of approximately 18-24 inches, or nearly double the range of travel that is possible in prior art image intensifier support systems. However, this extended range of travel of the image intensifier must be obtained through use of a support mechanism whose overall length is no greater than the overall length of the image intensifier itself when the image intensifier is positioned in the center of its permitted range of travel.
It is therefore a principal object of the present invention to provide an image intensifier support mechanism in which the image intensifier is supported for bi-directional travel over an extended range in a manner that insures its mechanical rigidity and stability over the entire range of travel and that does not allow the support mechanism to extend beyond either end of the image intensifier when the image intensifier is positioned in the center of its permitted range of travel. This and other objects are accomplished in accordance with the illustrated preferred embodiments of the present invention by providing a dual slide support mechanism in which a primary slide is bi-directionally driven over a primary range of travel by a rack and pinion arrangement and in which a secondary slide in telescoping relationship with the primary slide is bi-directionally driven in concert with the primary slide by stationary belts coupled over and under the primary slide between a fixed frame member and the secondary slide.